The overall objective of the proposed research is to quantify the neuromechanical influence of sensory feedback from the ankle joint over a range of speeds and gaits during cat locomotion. By studying how reflexes function across a range of speeds and gaits, we propose to partition out the relative contributions of peripheral modulation of reflexes at each activity level. Furthermore, we will elucidate a predictive relationship between reflex modulation and locomotion speed/gait. Self-reinnervation of certain muscle groups crossing the ankle joint will result in the effective loss of localized proprioceptive feedback. We will make biomechanical measurements during locomotion before and after self-reinnervation to determine their functional importance during locomotion. Biomechanical data will be quantified using high-speed video, 3-dimensional joint kinematics and linear algebraic analysis. The findings will provide valuable information about how reflexes are used during locomotion and how this importance changes across different speeds and gaits. This information can then be extrapolated to make predictions about how reflexes may be modulated to assist in rehabilitation techniques for human patients suffering from neurological diseases affecting motor control of movement and gait.